Is it permissible for a person who relies on others for his expenses to give charity from this money, and will his charity be accepted, especially if he is in debt?

It is permissible for a student to give charity to the poor or spend money in good causes if there is any surplus from what his family has given him, according to the Hadith: "Start with yourself and give charity to it. If there is a surplus, then it is for your family. If there is a surplus from your family, then it is for your relatives. If there is a surplus from your relatives, then it is for this and this (meaning other good causes)." It is also permissible for him to prioritize those in need if he knows himself to be patient. Otherwise, it is better for him to keep for himself what suffices him, for the Prophet said: "The best charity — or the most excellent charity — is that which is given when one is rich. The upper hand is better than the lower hand, and begin with those whom you support."

As for the debtor, if he wishes to give voluntary charity while he is in debt, the preferred view is that if he strongly believes that repayment will come from another source, then there is no harm in giving charity, and it may even be commendable. Otherwise, it is not permissible.